From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Vivier Subject: Re: [ANNOUNCE] kvm-14 release Date: Wed, 28 Feb 2007 15:12:22 +0100 Message-ID: <45E58DC6.4050107@bull.net> References: <45D98390.6060001@qumranet.com> <45DA25D9.1060509@aurel32.net> <45DA9FFA.2020009@qumranet.com> <45DB7514.3040409@aurel32.net> <45DBFD6E.2060507@qumranet.com> <45DC51E3.7010205@aurel32.net> <45DC54B5.9080608@qumranet.com> <45DC5D4E.5000300@bull.net> <45DC65C9.6010104@codemonkey.ws> <45DDC641.3030001@bull.net> <45DDC6F3.8080104@qumranet.com> <45DDD21F.4080202@codemonkey.ws> <45DDD30D.4000809@qumranet.com> <45DDDD01.7030802@us.ibm.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0422055472==" Cc: kvm-devel To: Anthony Liguori Return-path: In-Reply-To: <45DDDD01.7030802-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============0422055472== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigF94A52D8E57761FC38FB16D4" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF94A52D8E57761FC38FB16D4 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Anthony Liguori wrote: > Avi Kivity wrote: >> Anthony Liguori wrote: >>> Avi Kivity wrote: >>>> Laurent Vivier wrote: >>>>> There are remaining issues : libposix-aio uses kernel AIO, so files= =20 >>>>> must be >>>>> opened using O_DIRECT and buffers must be aligned. libposix-aio is = >>>>> able to >>>>> manage other cases but this has a performance cost. >>>>> >>>>> =20 >>>> Because the guest is also doing dma, the buffers are expected to be = >>>> aligned (it might be different if using pio, but unlikely). >>> The IDE emulation always uses a temporary buffer. This is partially = >>> because you cannot always rely on being able to use an offset on=20 >>> phys_ram_base (when doing user only emulation). >> Why is that? >=20 > Well, user won't do IDE emulation, but cpu_physical_memory_rw has to=20 > jump through more hoops for IDE. >=20 > What's more relevant though, is it's possible for the guest to setup DM= A=20 > to device memory, in which case, you need to route the IO to callbacks.= =20 > That's pretty unlikely though so I think we can stream line it so that = > we maintain correctness while also getting less copies. I'm not sure I had understood correctly your explanation, but I tried to = remove buffer from IDE device. I made a (pseudo-)benchmark with "dd" Applied patch is here: http://www.bullopensource.org/posix/qemu/ide-directio.diff (pseudo-)Benchmark is here: kvm-14 dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 4.735706 seconds (10811482 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 25.218732 seconds (20302369 bytes/sec) kvm-14 + libposix-aio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 3.335737 seconds (15348932 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 19.242217 seconds (26608161 bytes/sec) kvm-14 + libposix-aio + ide-directio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 2.695296 seconds (18996058 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 14.992513 seconds (34150379 bytes/sec) qemu-0.9.0 dd if=3D/dev/hda of=3D/dev/null count=3D100000 1200000 bytes transferred in 2.694546 seconds (19001345 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 25.524641 seconds (20059048 bytes/sec) qemu-0.9.0 + libposix-aio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 2.859584 seconds (17904702 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 25.045071 seconds (20443144 bytes/sec) qemu-0.9.0 + libposix-aio + ide-directio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 2.897503 seconds (17670387 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 25.900654 seconds (19767841 bytes/sec) qemu-0.9.0 + kqemu dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 6.204987 seconds (8251427 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 65.149972 seconds (7858791 bytes/sec) qemu-0.9.0 + kqemu + libposix-aio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 6.075537 seconds (8427239 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 57.506392 seconds (8903358 bytes/sec) qemu-0.9.0 + kqemu + libposix-aio + ide-directio dd if=3D/dev/hda of=3D/dev/null count=3D100000 51200000 bytes transferred in 6.083927 seconds (8415617 bytes/sec) dd if=3D/dev/hda of=3D/dev/null count=3D1000000 512000000 bytes transferred in 57.602499 seconds (8888503 bytes/sec) Regards, Laurent --=20 ------------- Laurent.Vivier-6ktuUTfB/bM@public.gmane.org -------------- "Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke --------------enigF94A52D8E57761FC38FB16D4 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.7 (GNU/Linux) iD8DBQFF5Y3L9Kffa9pFVzwRAhiCAKC0wv/ZfIcowS+2A0c5r6FvBuKuxACbB85Q QtzSOcdBPLyajxocWGZIf7k= =zESz -----END PGP SIGNATURE----- --------------enigF94A52D8E57761FC38FB16D4-- --===============0422055472== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline ------------------------------------------------------------------------- Take Surveys. Earn Cash. 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